Purification of kaolin clay by froth flotation

ABSTRACT

A method for removing finely divided particles of a colored titaniferous impurity from a dispersed alkaline pulp of kaolin clay by froth flotation. The collector for the impurities is a very low rosin acid tall oil which also provides controlled frothing without the addition of hydrocarbon oils to prevent overfrothing.

United States Patent [191 Mallary ['11] 3,827,556 [45] Aug. 6, 1974PURIFICATION OF KAOLIN CLAY BY FROTH FLOTATION [75] Inventor: Miller B.Mallary, Macon, Ga.

[73] Assignee: Engelhard Minerals & Chemicals Corporation, Woodbridge,NJ.

. 7/1958 Duke 3,635,337 l/l972 Mercade 209/166 X 3,640,382 2/l972 Jepsen209/166 FOREIGN PATENTS OR APPLICATIONS 598,311 5/1960 Canada 260/975Primary Examiner -Robert Halper Attorney, Agent, or Firm-Melvin C.Flint; Inez L. Moselle [57] ABSTRACT A method for removing finelydivided particles of a colored titaniferous impurity from a dispersedalkaline pulp of kaolin clay by froth flotation. The collector for theimpurities is a very low rosin acid tall oil which also providescontrolled frothing without the addition of hydrocarbon oils to preventoverfrothing.

5 Claims, No Drawings PURIFICATION OF KAOLIN CLAY BY FROTH FLOTATIONBACKGROUND OF THE INVENTION in various froth flotation processes. Theseoils are among the cheapest organic materials available and they areconsiderably less expensive than oleic acid and other pure higher fattyacids. In many cases, the impure tall oils are more selective than purefatty acids as collectors. It is well known, however, that the highrosin tall oils tend to cause overfrothing of alkaline flotation pulps,especially so in the case of slimey pulps. Overfrothing results indilution of mineral values by floating slimes when the values arerecovered in the froth. Low recoveries of mineral values are experiencedwhen the mineral values report in the flotation tailings,

To avoid the excessive, voluminous froth obtained when tall oil'is usedas a collector in a strongly alkaline pulp, it is common practice tomodify the flotation pulp by adding a neutral hydrocarbon oil tovcontrol the froth. In some cases, petroleum sulfonates may be used as asubstitute for a portion of the tall oil. However, even when thecombination of collectors is employed, it is usually essential to use aneutral oil to control the froth.

The factors discussed above have been instrumental in the selection of afour oil system for floating colored titania impurities from Georgiakaolinclay in commercial froth flotation. In the process, coloredimpurities, principally yellowish titaniferous impurities, are floatedfrom an alkaline dispersed pulp of impure kaolin clay with an anioniccollector and a calcite carrier. The collector reagent is a mixture of arelatively high rosin content tall oil (28 percent rosin acids) with anoilsoluble petroleum sulfonate. The two oils are added to adeflocculated alkaline clay pulp during conditioning. In order to curbthe froth which would be produced during conditioning, a neutral oil,preferably a lube oil, is added during conditioning. Flotation iscarried out on a continuous basis. The rougher froth which is aconcentrate of the carrier particles and the colored impurities issuccessively refloated in stages and the froth products from reflotationand scavengering may be impounded. The machine discharge products(tailings) are combined and contain the dispersed purified clay which isrecovered. During rougher and cleaner flotations a neutral hydrocarbonoil, preferably fuel oil, is added to the pulp in order to minimizelosses of clay in the froths. Typically 5-7 lbs/ton of a neutrallubricating type oil is added during conditioning and a total of 3lbs/ton of fuel type oil is added during flotation.

By such practices there is efficient removal of colored impurities atclay recoveries above 85 percent. However, in some instances traceresidues of the flotation oils contaminate the slip of flotationpurified clay and the clay will fail to respond to the expected extentto bleaching by a hydrosulfite salt (which is a conventional bleachreagent for clay).

Various methods have been suggested to remove the residual oils fromflotation beneficiated clay. However, these solutions merely compensatefor a problem and do not attack the source of the difficulty. It isapparent that there is a need for developing a clay flotation processwhich utilizes a reasonably inexpensive collector 2 which is adequatelyselective to the colored impurities in the clay and which obviates theneed to use neutral 7 oils for froth control purposes.

THE INVENTION An object of the invention is to provide an improvement ina process for removing colored impurities from kaolin clay whereby asingle oil may be used as the collector-frother.

Another object is to provide a method for floating titaniferousimpurities from kaolin clay which provides high yields of uncontaminatedpurified clay at a commercially feasible reagent cost.

The essence of my invention resides in subjecting a pulp of impurekaolin to froth flotation in the presence of tall oil containing 1percent to 5 percent rosin acids and the balance essentially a mixtureof unsaturated higher fatty acids as the sole oily reagent, the tall oilfunctioning both as the collector for the titania and to providecontrolled frothing. The use of this limited class of tall oils obviatesthe need for amultiple oil system while providing adequate collection oftitania and controlled frothing. The beneficiated clay has betterbrightness both before and after bleaching as a result of reducedreagent contamination. These results may be achieved without increasingthe cost of flotation reagents.

PRIOR ART The following US. patents disclose the use of various fattyacids or-tall oil acids as collectors for titania impurities in thefroth flotation of kaolin clay.

No. 2,569,680 Leek No. 2,990,958 Greene et a].

No. 3,224,582 lannicelli No. 3,450,257 Cundy No. 3,599,879 Clark No.3,151,062 to Duke is concerned with the problem of froth control in theflotation beneficiation of kaolin clay and is especially concerned withthe use of hydrocarbon oils to control frothing.

'The references above cited, as well as others cumulative thereto withregard to their disclosures of flotation collectors for a titaniferousimpurity in kaolin clay, fail to disclose or to suggest the inventiveconcept to which this patent application is directed.

DETAILED DESCRIPTION As used herein, the term tall oil is used inaccordance with widely accepted definition (A.S.T.M. D804-54) i.e., thenatural mixture of rosin acids related to abietic acid and of fattyacids related to oleic acid, together with nonacidic bodies, which isobtained by acidifying the black liquor skimmings of the alkaline paperpulp industry.. Crude tall oils usually contain from 28 percent topercent rosin acids and from about 5 percent to 24 percent nonacidbodies, depending upon the wood species which it is derived from.

The tall oils used in carrying out the present invention are obtained byrefining crude tall oil by distillation with recovery of a fattyacid-enriched fraction or by distillation plus other conventionalrefining such as acid treatment or adsorption to remove color bodies andoils. These refined tall oils are usually appreciably lower in nonacidbodies than crude tall oils and consist essentially of rosin acids andfatty acids, the fatty acids being present in proportions typical of theparent crude oils. Thus, the single flotation oil I employ tobeneficiated clay is a refined tall oil containing 1 percent to percent,preferably 2 percent to 4 percent rosin acids, the balance beingessentially a mixture of oleic acid and linoleic acid in weightproportions of about 50/50. Nonacid bodies (unsaponifiables) are-usuallybelow 2 percent. The combined fatty acid and rosin acid content of therefined tall oils I employ is usually 98 percent or above.

Tall oils containing less than 1 percent rosin acids lack theselectivity of tall oils having a higher rosin content and the use ofsuch highly refined oils is therefore outside the scope of my invention.Similarly, pure fatty acids such as oleic or linoleic acid, or mixturesthereof, have been found to be less selective than tall oils having asmall but significant rosin acid .content. Consequently, it is essentialto use an oily collector containing a small but limited amount of rosinacids. Further, the pure fatty acids and the essentially rosin-free talloil acids are considerably more expensive than the low rosin tall oilproducts I employ. On the other hand,

when the rosin content of a tall oil exceeds 5 percent, the clayrecovery is reduced in the absence of oily froth modifiers which Iexclude to avoid excessive contamination of the clay product. Tall oilproducts containing rosin acids in the preferred range of 2 percent'to 5percent by weight provide the best balance between clay recovery,selectivity and cost.

In putting my invention into practice, the low rosin tall oil may beused in acid form or the acids may be saponified before addition to thepulp. Alternatively the tall oil may be emulsified in a dilute solutionof ammonium hydroxide.

The preferred deflocculating agent for the clay pulp is sodium silicatewhich is preferably added as a dilute hydrosol, as described in MercadePat. No. 3,337,048.

The presently preferred flotation process uses a flotation carrier,preferably calcite, as described in U.S. Pat. No. 2,990,948. Suchprocess is hereinafter referred to as Ultraflotation. It is within thescope of the invention, however,'to omit the carrier, especially whenbeneficiating coarse kaolins or.when employing high energy conditioning(e.g., energy inputs of 50 hp. hr./ton or above).

The amount of low rosin tall oil used is generally within the range of 5to lbs./ton of dry clay when practicing Ultraflotation. When a carrierreagent is not employed, the quantity of the tall oil may be reduced,e.g., to 1 to 2 lbs/ton.

Conventional frothers, e.g., pine oil, are not required when using a lowrosin tall oil as the collector-frother in my process. I have found thatthe use of pine oil in conjunction with a low rosin tall oil reduced theyield of beneficiated clay.

The patents cited hereinabove provide detailed descriptions forpreparing kaolin clay crudes for flotation. Briefly, the steps involveblunging, degritting, particle size fractionation and deflocculation ofthe pulp. Procedures conventional in the flotation art may be used forconditioning and flotation. Reference is made to U.S. Pat. No. 2,990,958for details of the Ultraflotation process. As shown in this patent, thefroth from the rougher flotation is reconditioned without addition ofcollector and refloated to remove residual clay. The froth of thisflotation may be cleaned one or more times by reflotation. The finalfroth may be discarded. The

combined tailings, which contain the purified clay, are usuallyflocculated by addition of acid or alum and then the clay is bleached,filtered and washed. The bleach reagent used will depend upon the typeof clay employed. Conventional soft white clays may require only areduction bleach (e.g., a hydrosulfite salt). Gray kaolins may requiretreatment with a strong oxidant such as ozone or potassium permanganateprior to the reduction bleach unless the gray clay has been ozonated orotherwise oxidized prior to flotation.

The invention and its advantages will be better understood from theillustrative example which follows.

In the example, all brightness values were obtained by the conventionalTAPPI procedure (T-646 m-54). Quantities of reagents were reported aspounds per ton of dry clay in the clay pulp.

The clay used as the starting material in all tests was a softsedimentary Georgia kaolin crude representative of the clays used toprovide No. 1 coating clays. The crude was blunged in water at 40percent solids. The resulting pulp was partially dispersed by adding a 5percent solution of soda ash (2.2 lbs/ton), bringing pH to 7.5. To thepulp there was added as a deflocculant a hydrosol obtained by mixing a 5percent solution of N sodium silicate solution with a 1 percent solutionalum in amount corresponding to 6 lbs/ton N and 0.6 lb./ton alum. The pHwas about 8.5. The pulp was allowed to stand for 10 minutes to permitgrit to settle out and the supernatant was decanted. The decanted slipwas fractionated in a centrifuge and a slip of fine clay percent finerthan 2 microns) was recovered. All slips of clay used in the example hadbeen prepared in this manner.

EXAMPLE This example demonstrates the necessity for selecting a lowrosin acid oil in a single oil process for floating colored titania fromclay in order to obtain a high recovery of high brightness beneficiatedkaolin clay.

In tests carried out to study the effect of the rosin content of talloil on flotation parameters, oils containing 0 percent, 0.6 percent, 3.0percent, 7.0 percent, 26 percent and 45 percent were used. Since arosin-free tall oil was not available, it was synthesized by making a50/50 (wt.) blend of oleic acid and linoleic acid. The other oils werecommercial products which are characterized in Table I.

Portions of the slip of degritted fractionated clay at 20 percent solidswere conditioned for 22 minutes in a Fagergren conditioner with 400lbs/ton Drikalite (minus 325 mesh calcite), ammonium sulfate (5 percentsolution) added to pH 8.2, and 9 lbs/ton of one of the tall oil productsdescribed above. After conditioning the pH was adjusted to 8.6 withammonium hydroxide. No other oils or frothers were used. Flotation wascarried out in a batch laboratory cell for minutes. The underflow(machine discharge product or MD-1) of the flotation cell containing thepartially purified clay was Weighed to scertain yield f h 5 percent to26 percent. However, the high rosin acid rougher flotation. The frothfrom the rougher flotation system was impractical because of the lowclay yield. was diluted and cleaned by reflotation for 10 minutes. Thefroth was discarded and the underfl0 Data in Table 11 therefore showthat the Ultraflotawas recovered and weighed o determine recovery- Thetion could be carried out in the absence of a petroleum MDl and MD-2products Were com ined to pr 10 sulfonate or fuel oil modifiers withoutsacrificing clay the beneficiated clay slip. yield by using a commericaltall oil containing 3 per- A portion of each beneficiated slip Wa leachn cent rosin acids. When the oil contained less than 1 standard co ent amanne as o s- Th slips percent rosin acids, titania removal was lessthan could were acidified by addi g sulfuric acid o pH and n be obtainedwith 3 percent rosin acid and when the oil Zine hydrosulfite was ed in ao n of lbs/i011- 15 contained 7 percent rosin acid or more clayrecoveryv During bleaching, pH was maintained at 3.0 by addiwas i d ttion of sulfuric acid. Bleaching time was one-half hour. 1 i

Three runs were made for .each collector investi- 1. In a method forremoving discrete colored titanifgated. erous impurities from a finesize fraction of degritted Analyses of the flotation yields and kaolinclay wherein a dispersed alkaline pulp of the iml ached and unbleachedbrightness, n t ni pure clay is subjected to froth flotation in thepresence analysts are g p age values) in able II. r n anionic collectorfor the titaniferous impurities TABLE ll percent when rosin acid was 26percent. Unbleached brightness results reflected this trend. Bleachedbrightness (standard) increased from 90.4 percent to 90.9 percent whenrosin acid content was increased from 0 EFFECT OF ROSlN ACID CONTENT OFTALL OlLS ON FLOTATlON BENEFlClATlON OF KAOLlN CLAY SINGLE OlL-FROTHFLOTATION Weight Percent Brightness percent Flotation Yield Weightpercent TiO Unbleached Bleached Rosin In I Collector MD-l MD-2 Total a dOR" 0 76.3 11 3 87.6 0.53 87.5 90 4 90.6 0.6 71.5 18 5 90.0 0.49 85.090.2 90.6 3.0 60.0 27.3 87.3 0.43 85.6 90.4 91.1 7.0 44.5 29.3 73.8 0.4286.1 90.2 91.0 26.2 34.4 32.4 66.8 0.31 89.1 90 7 9l.l 43.0 32.3 37 770.0. 0.33 89.0 91 2 91.7 Control (no 1.64 81.0

flotation) 'zns o, ""KMnO +ZnS,O

Data in Table II for flotation yields obtained with tall oils of varyingrosin acid contents as the single flotation oil show that thev yield ofclay in the rougher flotation (MD-l) varied from 76 percent, when norosin was present, to only 32 percent, when the rosin acid content was43 percent. Overall recovery varied from 90.0 percent, when 0.6 percentrosin was present, to 70.0

percent with 43 percent rosin. The yield during rougher flotation was 60percent when the tall oil contained 3 percent rosin acids, whereas therougher yield was percent lower than this value when the tall oilcontained 7 percent rosin acids. Total yield was almost 15 percentgreater when the tall oil contained 3 percent rosin acids than it waswhen using tall oil with 7 percent rosin acids.

The results for yields on rougher and cleaner flotation clearly indicatethat when the rosin acid content of a tall oil is substantially inexcess of 3 percent, more flotation cells will be required to clean theclay and the recovery of beneficiated clay will be less than when usingtall oils containing less rosin acids.

Titania analyses in the table show that titania removal was directlyrelated to the rosin content of the oily collector. When the collectorwas free from rosin, 68 percent TiO was removed This was increased to 81and means is provided for imparting controlled frothing characteristicsto the pulp, the improvement which consists of using as the collectorfor the impurities a refined low rosin tall oil product containing 1percent to 5 percent by weight rosin acids and the balance substantiallya mixture of oleic acid and linoleic acid, said low rosin tall oilproduct also serving to provide controlled frothing characteristics,said low rosin talloil product being the sole flotation oil added to thepulp.

2. The method of claim 1 wherein the rosin acid content is within therange of Z'percent to 4 percent by weight.

3. The method of claim 1 wherein the flotation is carried out in thepresence of added minus 325 mesh calcite particles to aid in theflotation of the titania impurities and said tall oil is used in amountwithin the range of 5 to 10 lbs./ton of clay in the flotation pulp.

4. The method of claim 3 wherein said fine size fraction is aboutpercent by weight less than 2 microns.

5. The method of claim 4 wherein the pulp containing the impure finesize fraction of clay and calcite is conditioned in a single stage withsaid tall oil.

t i I! I

2. The method of claim 1 wherein the rosin acid content is within therange of 2 percenT to 4 percent by weight.
 3. The method of claim 1wherein the flotation is carried out in the presence of added minus 325mesh calcite particles to aid in the flotation of the titania impuritiesand said tall oil is used in amount within the range of 5 to 10 lbs./tonof clay in the flotation pulp.
 4. The method of claim 3 wherein saidfine size fraction is about 90 percent by weight less than 2 microns. 5.The method of claim 4 wherein the pulp containing the impure fine sizefraction of clay and calcite is conditioned in a single stage with saidtall oil.